Spark-plug



J. A. LUTHER.

SPARK PLUG.

APPLICATION FILED IuLY 25,19I9.

Patented June 7, 1921.

Z. s .WJ I nF P. 5 H m 3 8 5 i I A lvenCoT John A. Luher .man A. LUTHER,or scnmmc'ranr. NEW vom;

Patented June 7, 19211.

L Application lled July 25, v1911?. Serial No. 313,342.

SPARK-PLUG. 1,380,399 Specication of Letters Patent To all whom t mayconcern.'

Be it known that .I, JOHN A. LUTHER, a citizen of the United. States,residing at Schenectady, in the countyl of Schenectady, State of NewYork, havlevinventedcertain new and' useful Improvements in Spark-Flugs, ofvwhich the following isa specificatlon:

The present `invention relates to spark plugs for internal combustionengines and has for its object to improve their construction. Myimprovements arevdirected prin- /bipally to the means forsupporting theporcelain .or other insulator for the central electrode whereby thebreakage thereof bothin -manufacture and use will be decreased to aminimum, and also to the means for insuring airtightv vseals between theporcelain or other insulator and its metal support or K shell andbetweenthe central electrode and the surrounding insulator. Additional'features of my invention are the means for protecting the insulatorfrom injury when the plug'is being screwed into or removed from theengine cylinder, and the arrangement forv conveying heatfaway from'theinterior parts of the plug.

Fora consideration of-what I believe to be novel and .my invention,vattention is directed to the accompanying description and claimsappended thereto.

In the drawing, Figure 1 is a viewin elevation of a spark plugwith aportion of the casing cut away in quarter section and Fig. 2 is an axialsection-of the same.

5 indicatesthe metal shell or casing ofthe plug which is threadedat oneend to enable it to be screwed into the engine cylinder or 'othersupportIt is provided with the usual flange orshoulder 6 between which and thecylinder or support is located a suitable packing or gasket, not shown.The opposite end of the shell is provided' with a hexagon head 7 toreceive a suitable Wrench. y Inside theshell is an annular shoulder 8upon which the porcelain or other insulator 9 is seated. The head of theshell is also internally threaded to receive the tubular meniber' 10which has several functions. 'First it acts as an abutment for the shockabsorbing' coiled compression spring 11 which Jholds the insulator onits seat;l second it acts ras a guard to prevent injury to theinsulator; third it acts as a. guide for the outer portlon of theinsulator; and fourth it parts, and hence definitely limits the'tensionon the spring to a predetermined. value. It is to'be particularly notedthat the inner-end 13 of the member does not contact with the insulatorin any way and therefore cannot cause any cracking or undue strainsthereon when screwed into place, no matter how careless the assemblermay be or how much pressure is employedin securingv the parts together.rIhe shoulder has two flat surfaces to receive a wrench, one of which isindicated' at 14. I l I The outer end of the member is provided with aninternal shoulder `15 which acts` as absorbing coiled vcompressionspring 11. The spring is preferablymade of Hat stock ince'it permits thedesired'sprng tension o be 'obtained without making the diameter undulylarge. It is important not only from a manufacturing point of view tomake the diameter as small as possible but also to facilitate mountingLthe plugin the engine. The insulator, it will-be noted, is cylindricalwith a shoulder or an enlarged portion 16 which rests on the internalshoulder'on the shell, there being a copper or equivalent gasket 17 toforma seal. The .opposite side of the enlargedportion is also providedwith a copper or .the inner end of the spring rests. The spring whenmounted in place should be under sufficientcompression to hold theinsulator on its seat even when it is subjected' to the .high pressureof the burning charge of combustible in the cylinder. The spring will,however, compensate for changes due to different rates of expansion ofthe parts L and also absorb shocks to' which the plug is subjected.while in operation.

It is `to f be particularly noted that any shocks to which the insulatoris subjected.

due to the firing of the charge in the' cylin-v .der are absorbed by thespring instead of being directly transmitted to the casing, and hencebreakage .of the insulator is prevented.

In practicethe springs are cut to the desired' length and their endsproperly finished so as to seat squarely on the insulator at equivalentgasket 18 upon which,

' latter being guided the ordinary construction.

-heated andv losing its f- In case the plug gets foul the central elecvoccur to the insulator because there are no non-yielding parts whichGrip it' as in lhe assembler merely screws the member to its seat an thespring does the rest, the tension ot the latter having been previouslydetermined.` rl`his means that nothing is left to the individual skillof the assembler and the bugbear of loose or cracked insulators isovercome.`

The central electrode 19, is provided With a collar 20 which is seatedona shoulder on the insulator, and betweenv the collar and` and shoulderis a Washer or gasket to maintain an air tight seal. The inner end ofthe electrode projects beyond the inner part of the shell and standingadjacent to it but separated by a suitable air gap is a second electrode2l carried by the shell and grounded of course, to the engine. yTheouter end of the center electrode 19 is screwfthreaded and passesthrough a secondary insulator 22, the or held central by the bore of theinternal shoulder on the member. Between the main and secondaryinsulators there'is or may be a suitable gasket 23 which serves as anadditional means to prevent the escape of gas from the cylinder. aroundthe central electrode. 0n the electrode and outside the insulator 22 isa clamping mit 24 which may With advantage be made round and adjusted bya pair of pliers. Under the nut is a lock Washer 25, and below that acopper or other disk. Over the nut 24 is a second nut 25a which acts asa lock-nutv for the irst and also as a seat for the ignition lead whichis connected to the plug and to a source of current. 26 indicates thenut for holding the lead in place. By arranging the nut 24 as describedthere is no danger of a careless person accidentally disturbing theclamping device 24 of the central electrode which would permit air toleak around it into the cylinder.

In order to keep the internal plug from becoming unduly hot,

parts of the the head of the shell is provided With ventilating open.

ings 27 which arev adjacent the enlarged part of the main insulator.Other Ventilating openings 28 are provided in the tubular member andthrough all of the ogenmgs air is permitted to freely circulate.

preventing the spring from being overtemper.

t'rode can be removed from the under side for cleaning by removing thenuts 24, 25 and 26. The main insulator is not disturbed because itisheld in position by the compression spring and the tubular member.- By

tionary L provided with shoulder and o'rming n particular, theVentilating arrangement isvuseful in shell Which is screw-t readedexternally at 1,3eo,eee

this arrangement the chance of injurying the porcelain or main insulatoris reduced to a minimum.

In accordance patent statutes, I ple of operation ofl my with theprovisions of the have described the princiinvention, together With theapparatus Which I now consider to -represent by Letters Patent of theUnited States is -A 1. 1n a spark plug, the combination of a shelladapted to be-attached to a support and provided With an internalshoulder, av

stationary insulator mounted Within the shell and having an enlargedportion Which is seated on the shoulder, a shockabsorbing compressionspring which surrounds the insula'tor and forms the means for holding iton its seat against cylinder pressure, an abutment for the outer end dithev spring, a sta- 'electrode Which passes insulator and is adapted tobe connected to a source of current, and a second electrode have itunderstood that the appathrough the coperatingfwith the first andpermanently separated therefrom by an air gap.

2. 1n a spark plug, the combination of a shell which is screw-threadedexternally for attachment to a support and has an internal shoulder,aninsulator which has an enlarged portion on -`the shoulder, a coiledcompres-` sion spring which surrounds the, insulator and holds it on itsseat against cylinder pres.- sures, a member for the outer-end ofthespring and is attached to the shell, an electrode Which passes throughthe insulator, anda second electrode supported by the shell.

3. 1n a spark plug, the combination of a 'shell which is screw-threadedexternally at one end and internally` at the other, and is tionaryinsulator which is seated on the a gas-tight seal, a member whichsurrounds therinsulator and is screw-seated on the shell at oneend andhas an internal flange at they other, a shock absorbing compressionspring'which -holds an internal shoulder, astawhich forms an abutmentthe insulator on its seat against cylinder` pressure and in turn isheld'under compression by theflange, and passes through the insulatorfrom end to end and is permanently separated from the shell by an airgap.

4. 1n; a spark plug, the combination of a one end 4and internally at theother, and 1s provided with an internal shoulder, a stationary insulatorwhich is seated on the shoulder,

an electrode which' a member which surrounds the.

insulator and is screw-threaded at one end for attachment to the shell,carries a-sprlng abutment,` and has an, external Shoulder t,displacement and forms a part of an elec-v which is seated on the outerend of the shell, a shock absorbing compression spring which rests onthe insulator at one end to hold it on. its seat against cylinderpressure and at the other end engages the abutment, the tension of thespringv being determined by said shoulder, and a stationary electrodewhich passes through the insulator and is permanently separated from theshell by an air gap.

5. In a spark plug, the combination of a screw-threaded shell, having aninternal shoulder, an insulator which engages the shoulder, a tubularmember screw-threaded to the shell and inclosing the insulator, a coiledcompression spring which holds the insulator on its seat againstcylinder pressure and is retained under compression by the member, andVentilating passages formed in the shell and member through which air isfree to flow over the spring.

6. In a spark plug, the combination of a screw-threaded shell having aninternal shoulder, an insulator mounted on the shoulder, a member whichincloses the insulator and is attached to the shell, a spring within themember which holds the insulator on its seat, a secondaryinsulatorsupported by the first and guided by the member, and anelectrode which passes through both insulators, is seated pressure tightin one and forms a means for uniting both.

7. In a spark plug, the combination of a screw-threaded shell having aninternal shoulder, an insulator mounted on the shoulder, a member whichincloses-the insulator and is attached to the shell, a spring within themember which holds the insulator on its seat, a secondary insulatorsupported by the first and guided by the member, an electrode whichpasses through both insulators and is seated pressure tight, a nut onthe electrode which clamps the two insulators `together, and a secondnut on the electrode which covers the rst to prevent accidental tricterminal.

8. In a spark plug, the combination of a shell adapted to be attached tothe engine and which is provided with an internal shoulder, an insulatorhaving an enlarged portion which is seated on the shoulder, a memberthreaded to the shell which surrounds the insulator and is spaced thereastationary insulator which is provided with an enlargement between itsends, the under surface of which is supported by the shoulder, a tubularmember which has screw threads that engage those at the outer end of theshell and also a spring abutment, means for limiting the amount that themember can be screwed downward with respect to the shell, a shockabsorbing spring which surrounds the insulator, one Vend of said springpressing on the enlargement on the insulator, the other end engaging theabutment, an electrode which passes through the insulator, and a secondelectrode which is supportedl by the shell and separated from the lirstby a permanent air gap.

10. In a spark plug, the combination of a metal shell which isscrew-threaded at opposite ends and has an internal shoulder, a gasketwhich rests on the shoulder, a stationary porcelain insulator which hasa shoulder that `is seated on the gasket, a hollow member whichsurrounds the insulator, has screw threads which engage those on theouter end of the shell and also an internal spring abutment, a shock.absorbing spring which surrounds the outer portion .of the insulatorand presses on its shoulder at one end and engages said abutment at theother, means for limiting lthe amount that the member can be screweddownward with respect to the shell, thereby definitely limiting thepressure that the spring can exert on the insulator, and an electrodewhich extends centrally through the insun lator and is permanentlyseparated from the inner end of the shell by a permanent air gap. p

In witness whereof, I have hereunto set my hand this 23rd day of July,1919.

JOHN A. LUTHER

